Pulsed plasma deposition etch step coverage improvement

ABSTRACT

Embodiments of the present disclosure relate to methods for in-situ deposition and treatment of a thin film for improved step coverage. In one embodiment, the method for processing a substrate is provided. The method includes forming a dielectric layer on patterned features of the substrate by exposing the substrate to a gas mixture of a first precursor and a second precursor simultaneously with plasma present in a process chamber, wherein the plasma is formed by a first pulsed RF power, exposing the dielectric layer to a first plasma treatment using a gas mixture of nitrogen and helium in the process chamber, and performing a plasma etch process by exposing the dielectric layer to a plasma formed from a gas mixture of a fluorine-containing precursor and a carrier gas, wherein the plasma is formed in the process chamber by a second pulsed RF power.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 62/687,100, filed on Jun. 19, 2018, which herein isincorporated by reference.

FIELD

Embodiments of the present disclosure generally relate to methods forsemiconductor processing. Specifically, embodiments of the presentdisclosure relate to methods for in-situ deposition and treatment of athin film for improved step coverage.

BACKGROUND

Dielectric layers have been used for applications such as barrier layersor spacers in the fabrication of modern semiconductor devices. Thedielectric layers can be deposited over features, e.g., trenches or viasused for vertical interconnects, using a deposition process, such aschemical vapor deposition (CVD) or plasma enhanced chemical vapordeposition (PECVD). However, it has been challenging to deposit thedielectric layers over high aspect ratio features with adequate stepcoverage by the PECVD technique. The PECVD technique tends to depositthe dielectric layer more rapidly around the top than the bottom of thetrenches due to the inability of the plasma to penetrate into the deeptrenches. This results in pinching-off the narrow trenches from the top,forming a void in the trenches.

Therefore, there is a need in the art to provide an improved method fordepositing dielectric layers in high aspect ratio trenches withoutforming voids or seams.

SUMMARY

Embodiments of the present disclosure relate to methods for in-situdeposition and treatment of a thin film for improved step coverage. Inone embodiment, the method for processing a substrate is provided. Themethod includes forming a dielectric layer on patterned features of thesubstrate by exposing the substrate to a gas mixture of a firstprecursor and a second precursor simultaneously with plasma present in aprocess chamber, wherein the plasma is formed by a first pulsed RFpower. The method further includes exposing the dielectric layer to aplasma treatment using a gas mixture of nitrogen and helium in theprocess chamber, and performing a plasma etch process by exposing thedielectric layer to a plasma formed from a gas mixture of afluorine-containing precursor and a carrier gas, wherein the plasma isformed in the process chamber by a second pulsed RF power.

In another embodiment, a method for processing a substrate includesforming a dielectric layer on patterned features of the substrate by aplasma deposition process, wherein a first plasma is formed by a firstpulsed RF power in a process chamber. The method further includesdensifying the dielectric layer by a plasma treatment, and etching aportion of the dielectric layer by a plasma etch process, wherein asecond plasma formed from a gas mixture of a fluorine-containing gas anda carrier gas, wherein the second plasma is formed in the processchamber by a second pulsed RF power.

In another embodiment, a method for processing a substrate includesforming a dielectric layer on patterned features of the substrate by aplasma deposition process, wherein a first plasma is formed by a firstpulsed RF power in a process chamber. The method further includesdensifying the dielectric layer by a plasma treatment using a gasmixture of nitrogen and helium in the process chamber, forming a firstpassivation layer on the dielectric layer, etching the first passivationlayer and a portion of the dielectric layer by a plasma etch process toform a etched dielectric layer, wherein a second plasma is formed in theprocess chamber by a second pulsed RF power. The method further includesforming a second passivation layer on the etched dielectric layer.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure, briefly summarized above anddiscussed in greater detail below, can be understood by reference to theillustrative embodiments of the disclosure depicted in the appendeddrawings. It is to be noted, however, that the appended drawingsillustrate only typical embodiments of this disclosure and are thereforenot to be considered limiting of its scope, for the disclosure may admitto other equally effective embodiments.

FIG. 1 depicts a schematic cross-sectional view of a deposition systemthat can be used for the practice of embodiments described herein.

FIGS. 2A and 2B depict a flow diagram of a method for forming adielectric layer over a substrate in accordance with embodiments of thepresent disclosure.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. The figures are not drawn to scale and may be simplifiedfor clarity. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

Embodiments described herein will be described below in reference to aPECVD process that can be carried out using any suitable thin filmdeposition system. Examples of suitable systems include the CENTURA®systems which may use a DXZ® processing chamber, PRECISION 5000®systems, PRODUCER® systems, PRODUCER® GT™ systems, PRODUCER® XPPrecision™ systems, PRODUCER® SE™ systems, Sym3® processing chamber, andMesa™ processing chamber, all of which are commercially available fromApplied Materials, Inc., of Santa Clara, Calif. Other tools capable ofperforming PECVD processes may also be adapted to benefit from theembodiments described herein. In addition, any system enabling the PECVDprocesses described herein can be used to advantage. The apparatusdescription described herein is illustrative and should not be construedor interpreted as limiting the scope of the embodiments describedherein.

FIG. 1 depicts a schematic illustration of a substrate processing system132 that can be used to perform deposition of a dielectric layer inaccordance with embodiments described herein. The substrate processingsystem 132 includes a process chamber 100 coupled to a gas panel 130 anda controller 110. The process chamber 100 generally includes a top wall124, a sidewall 101 and a bottom wall 122 that define a processingvolume 126. A substrate support assembly 146 is provided in theprocessing volume 126 of the process chamber 100. The substrate supportassembly 146 generally includes a substrate support, such as anelectrostatic chuck 150, supported by a stem 160. The electrostaticchuck 150 may be moved in a vertical direction inside the processchamber 100 using any suitable mechanism. An electrode 170 is embeddedin the electrostatic chuck 150, and a power source 106 is coupled to theelectrode 170. A substrate 190 is disposed on a surface 192 of theelectrostatic chuck 150.

A vacuum pump 102 is coupled to a port formed in the bottom of theprocess chamber 100. The vacuum pump 102 is used to maintain a desiredgas pressure in the process chamber 100. The vacuum pump 102 alsoevacuates post-processing gases and by-products of the process from theprocess chamber 100. The substrate processing system 132 may furtherinclude additional equipment for controlling the chamber pressure, forexample, valves (e.g., throttle valves and isolation valves) positionedbetween the process chamber 100 and the vacuum pump 102 to control thechamber pressure.

A gas distribution assembly 120 having a plurality of apertures 128 isdisposed on the top of the process chamber 100 above the electrostaticchuck 150. The apertures 128 of the gas distribution assembly 120 areutilized to introduce process gases into the process chamber 100. Theapertures 128 may have different sizes, number, distributions, shape,design, and diameters to facilitate the flow of the various processgases for different process requirements. The gas distribution assembly120 is connected to the gas panel 130 that allows various gases tosupply to the processing volume 126 during processing. A plasma isformed from the process gas mixture exiting the gas distributionassembly 120 to enhance thermal decomposition of the process gasesresulting in the deposition of material on a surface 191 of thesubstrate 190.

The gas distribution assembly 120 and the electrostatic chuck 150 mayform a pair of spaced apart electrodes in the processing volume 126. Oneor more RF power source 140 provide a bias potential through a matchingnetwork 138, which is optional, to the gas distribution assembly 120 tofacilitate generation of plasma between the gas distribution assembly120 and the electrostatic chuck 150. Alternatively, the RF power source140 and the matching network 138 may be coupled to the gas distributionassembly 120, the electrostatic chuck 150, or coupled to both the gasdistribution assembly 120 and the electrostatic chuck 150, or coupled toan antenna (not shown) disposed exterior to the process chamber 100. Insome embodiments, the RF power source 140 may produce power at afrequency of 350 KHz, 2 MHz, 13.56 MHz, 27 MHz, 40 MHz, 60 MHz, or 100MHz. In one embodiment, the RF power source 140 may provide betweenabout 100 Watts and about 3,000 Watts at a frequency of about 50 kHz toabout 13.6 MHz. In another embodiment, the RF power source 140 mayprovide between about 500 Watts and about 1,800 Watts at a frequency ofabout 50 kHz to about 13.6 MHz.

The controller 110 includes a central processing unit (CPU) 112, amemory 116, and a support circuit 114 utilized to control the processsequence and regulate the gas flows from the gas panel 130. The CPU 112may be of any form of a general-purpose computer processor that may beused in an industrial setting. The software routines can be stored inthe memory 116, such as random access memory, read only memory, floppy,or hard disk drive, or other form of digital storage. The supportcircuit 114 is conventionally coupled to the CPU 112 and may includecache, clock circuits, input/output systems, power supplies, and thelike. Bi-directional communications between the controller 110 and thevarious components of the substrate processing system 132 are handledthrough numerous signal cables collectively referred to as signal buses118, some of which are illustrated in FIG. 1.

FIGS. 2A and 2B depict a flow diagram of a method 200 for forming adielectric layer over a substrate in accordance with embodiments of thepresent disclosure. All of the operations of the method 200 may beperformed in the same process chamber, such as a PECVD chamber. Itshould also be understood that the operations depicted in FIG. 2 may beperformed simultaneously and/or in a different order than the orderdepicted in FIG. 2. In addition, while the dielectric layer is discussedherein using a PECVD technique, the concept of this disclosure can alsobe utilized towards other layers that are deposited by a thermal processor any plasma-assisted process.

The method 200 begins at operation 202 by placing a substrate into aprocess chamber, such as the process chamber 100 shown in FIG. 1. Afterthe substrate is disposed in the process chamber 100, an in-situdeposition-treatment process 203 is performed in the process chamber100. As will be discussed in more detail below, the in-situdeposition-treatment process 203 generally includes operation 204 (filmdeposition), operation 206 (chamber purging), operation 208 (plasmatreatment), and operation 210 (chamber purging). The substrate may be apatterned substrate having at least one formed feature across a surfacethereof. The formed feature may be any type of feature such as a trench,via, interconnect, or gate stack, for example. The substrate may be aportion of an intermediate structure of a semiconductor device, such asa FinFET device. The substrate may be a bulk semiconductor substrate, asemiconductor-on-insulator (SOI) substrate, or the like, which may bedoped (e.g., with a p-type or an n-type dopant) or undoped. Thesubstrate may include an elemental semiconductor including silicon (Si)or germanium (Ge); a compound semiconductor; an alloy semiconductor; ora combination thereof. In one embodiment, the substrate has a pluralityof trenches formed in the surface of the substrate. The trenches mayhave an aspect ratio of about 2:1 to about 20:1, for example about 3:1to about 10:1. The term “aspect ratio” in this disclosure refers to theratio of the height dimension to the width dimension of a particularfeature, for example, trench height/trench width.

At operation 204, a dielectric layer is formed on the substrate using aplasma deposition process. In one embodiment, the dielectric layer is anitride, such as a silicon nitride. The dielectric layer is formed onexposed surfaces of the substrate, for example, the top surface, thesidewall surface, and the bottom surface of the trenches in thesubstrate. The deposition of the dielectric layer is performed byexposing the substrate to a gas mixture of a nitrogen-containingprecursor and a silicon-containing precursor simultaneously with plasmapresent in the process chamber. The gas mixture may be flowed from thegas panel 130 into the processing volume 126 through the gasdistribution assembly 120. In some cases, the nitrogen-containingprecursor and the silicon-containing precursor may be introduced intothe process chamber separately and can be in any sequence order.Depending on the application, the gas mixture may optionally includehelium, nitrogen, oxygen, nitrous oxide, argon, or any suitable inertgas or carrier gas.

Suitable nitrogen-containing precursor may include ammonia (NH₃),nitrogen (N₂), nitrous oxide (N₂O), nitric oxide (NO), nitrogen dioxide(NO₂), and any combination thereof. In one embodiment, thenitrogen-containing precursor is ammonia. Suitable silicon-containingprecursor may include organosilicon compounds having a ratio of oxygento silicon atoms of 0 to about 6. Suitable organosilicon compounds maybe siloxane compounds, halogenated siloxane compounds that include oneor more halogen moieties (e.g., fluoride, chloride, bromide, or iodide),such as tetrachlorosilane, dichlorodiethoxysiloxane,chlorotriethoxysiloxane, hexachlorodisiloxane, and/oroctachlorotrisiloxane, and aminosilanes, such as trisilylamine (TSA),hexamethyldisilazane (HMDS), silatrane, tetrakis(dimethylamino)silane,bis(diethylamino)silane, tris(dimethyl-amino)chlorosilane, andmethylsilatrane. Other silicon-containing precursors, such as silanes,halogenated silanes, organosilanes, and any combinations thereof, mayalso be used. Silanes may include silane (SiH₄) and higher silanes withthe empirical formula Si_(x)H_((2x+2)), such as disilane (Si₂H₆),trisilane (Si₃H₆), and tetrasilane (Si₄H₁₀), or other higher ordersilanes such as polychlorosilane. Other silicon-containing precursor,such as octamethylcyclotetrasiloxane (OMCTS), methyldiethoxysilane(MDEOS), bis(tertiary-butylamino)silane (BTBAS), tridimethylaminosilane(TriDMAS), trisdimethylaminosilane (TrisDMAS), dichlorosilane,trichlorosilane, dibromosilane, silicon tetrachloride, silicontetrabromide, or combinations thereof, may also be used. In oneembodiment, the silicon-containing precursor is silane. In anotherembodiment, the silicon-containing precursor is TSA.

During operation 204, the silicon-containing precursor may be introducedinto the process chamber at a flow rate of between about 5 sccm andabout 1000 sccm. The nitrogen-containing precursor may be introducedinto the process chamber at a flow rate of between about 5 sccm andabout 1000 sccm. An optional carrier gas, e.g., helium, may beintroduced into the process chamber at a flow rate of between about 100sccm and about 20000 sccm. The chamber pressure may be maintained atabout 5 mTorr or greater, such as about 1 Torr to about 40 Torr, forexample about 5 Torr to about 16 Torr, and the temperature of asubstrate support in the process chamber may be between about 125° C.and about 580° C., for example about 150° C. to about 400° C., while thesilicon-containing precursor and the nitrogen-containing precursor areflowed into the process chamber to deposit the dielectric layer. Theplasma deposition process may be performed for about 2 seconds to about120 seconds, for example about 6 seconds to about 30 seconds, which mayvary depending upon the application.

The plasma may be provided at about 50 Watts to about 250 Watts of RFpower at a frequency of 13.56 MHz and/or 350 KHz. The RF power may beprovided to one or more electrodes of the process chamber 100. Forexample, the RF power may be provided to a showerhead, e.g., the gasdistribution assembly 120, and/or a substrate support, e.g., theelectrostatic chuck 150 of the process chamber 100. In some embodiments,the RF power is pulsed during the plasma deposition process to reducethe deposition rate of the dielectric layer on exposed surfaces of thetrenches, thereby improving the sidewall step coverage of the dielectriclayer in the trenches. The RF power can be pulsed with a duty cycle in arange from about 5% to about 30% and at a frequency in a range fromabout 10 kHz to about 20 kHz. The spacing between the showerhead and thesubstrate support may be greater than about 230 mils, such as betweenabout 350 mils and about 800 mils.

At operation 206, the flow of the gas mixture into the process chamber100 and the RF power are stopped, and any remaining gas mixture (e.g.,silicon-containing precursor, nitrogen-containing precursor, and/oradditional gas) is purged from the process chamber 100 by introducing apurge gas, such as nitrogen gas, into the process chamber 100. The purgegas is introduced into the process chamber at a time period and partialpressure that are selected to purge the residual gas mixture and/or theresidual by-products. For example, the purge gas may be introduced intothe process chamber at a flow rate of between about 100 and about 20000scorn. The nitrogen gas may be flowed into the chamber for a period oftime such as between about 0.1 seconds and about 60 seconds. The chamberpressure may be between about 5 mTorr and about 10 Torr, and thetemperature of the substrate support in the process chamber 100 may bebetween about 125° C. and about 580° C. while the purge gas is flowedinto the process chamber.

At operation 208, after the process chamber is purged, a plasmatreatment is performed in the process chamber 100 to treat the depositeddielectric layer. The plasma treatment can densify the depositeddielectric layer and improve the mechanical properties of the depositeddielectric. For example, a modulus (Young's modulus) or hardness of thedeposited dielectric layer can be increased after the plasma treatment.The improved mechanical properties allow the treated dielectric layer tosustain the harsh environment during the subsequent etch process withthe required profile and/or conformity.

The plasma treatment may be performed by introducing a treatment gasmixture of nitrogen and helium into the process chamber 100 at a flowrate of between about 100 and about 20000 sccm. The ratio of thenitrogen and helium may be in a range of about 1 (nitrogen):3 (helium)to about 1 (nitrogen):10 (helium), for example about 1 (nitrogen):6(helium). The nitrogen gas may be introduced into the process chamber ata flow rate of between about 100 and about 2000 sccm. The treatment gasmixture may be flowed into the process chamber for a period of time suchas between about 0.1 seconds and about 120 seconds. The plasma may beprovided by applying a RF power of between about 300 Watts and about1200 Watts to the process chamber at a frequency of 13.56 MHz and/or 350KHz. The chamber pressure may be between about 4 Torr and about 12 Torr,and the temperature of the substrate support in the process chamber 100may be between about 125° C. and about 580° C. while the treatment gasmixture is flowed into the process chamber.

At operation 210, the plasma treatment is terminated and the processchamber is purged to remove the residual gas mixture and/or the residualby-products. The plasma treatment may be terminated by interrupting theRF power and the flow of the treatment gas mixture into the processchamber. The purging at operation 210 can be similar or identical tooperation 206.

At operation 212, a decision is made as to determine whether thedeposited dielectric layer that has been plasma treated reaches a targetthickness. The deposited/treated dielectric layer may have a targetthickness of about 5 Å to about 2000 Å, for example about 150 Å, whichmay vary depending upon the application. If the target thickness of thedeposited/treated dielectric layer has not been reached, another cycleof deposition/plasma treatment process (e.g., operations 204, 206, 208and 210) may be performed before the thickness of the deposited/treateddielectric layer is again compared to the target thickness. The in-situdeposition-treatment process 203 is repeated until the deposited/treateddielectric layer reaches the target thickness.

Once the deposited/treated dielectric layer reaches the targetthickness, an in-situ plasma etch/treatment process 213 is performed inthe process chamber 100. As will be discussed in more detail below, thein-situ plasma etch/treatment process 213 generally includes operation214 (plasma etch), operation 216 (chamber purging), operation 218(treatment), and operation 220 (chamber purging).

Prior to the in-situ plasma etch/treatment process 213 and afteroperation 212, the deposited/treated dielectric layer may be optionallypassivated. At operation 211, an optional treatment is performed in theprocess chamber 100 to form a passivation layer on the dielectric layer.After operation 212, either the treatment process to form thepassivation layer on the dielectric layer (operation 211) or the plasmaetch process (operation 214) is performed. The optional treatment may beperformed by exposing the dielectric layer to a silicon-containingprecursor in the process chamber to form a thin silicon layer on thedielectric layer. Depending on the application, the dielectric layer maybe exposed to additional gas or gases, such as helium, nitrogen, oxygen,nitrous oxide, argon, or any suitable inert gas or carrier gas. Suitablesilicon-containing precursor may be similar or identical to thesilicon-containing precursor used during operation 204. In oneembodiment, the silicon-containing precursor is silane. In anotherembodiment, the silicon-containing precursor is TSA.

During operation 211, the silicon-containing precursor may be introducedinto the process chamber at a flow rate of between about 5 sccm andabout 1000 sccm. In some embodiments, a nitrogen-containing gas isintroduced into the process chamber with the silicon-containingprecursor, and the nitrogen-containing gas may be introduced into theprocess chamber at a flow rate of between about 5 sccm and about 1000sccm. An optional carrier gas, e.g., helium, may be introduced into theprocess chamber at a flow rate of between about 100 sccm and about 20000sccm. The chamber pressure may be maintained at about 5 mTorr orgreater, such as about 1 Torr to about 40 Torr, for example about 5 Torrto about 16 Torr, and the temperature of a substrate support in theprocess chamber may be between about 125° C. and about 580° C., forexample about 150° C. to about 400° C., while the silicon-containingprecursor is flowed into the process chamber to deposit the siliconlayer. In one embodiment, the silicon layer includes silicon moleculesadsorbed on the dielectric layer. The optional treatment may beperformed for about 1 seconds to about 60 seconds, for example about 2seconds to about 30 seconds, which may vary depending upon theapplication. The treatment helps the subsequent etch process to be a“soft” etch process. “Soft” etch is referring to when the etchant such afluorine ions or fluorine containing radicals attack the passivationlayer on top of the dielectric layer, and the passivation layer reducesthe impact of the fluorine ions or fluorine containing radicals andsurface etching is thereby carried out. The additional benefit of thepassivation layer can also impact the etch profile and improve theaspect ratio of the dielectric layer in the trench.

At operation 215, the treatment process is terminated and the processchamber is purged to remove the residual silicon-containing precursorand other gases. The treatment process may be terminated by interruptingthe flow of the silicon-containing precursor into the process chamber.The purging at operation 215 can be similar or identical to operation206.

The in-situ plasma etch/treatment process 213 starts at operation 214, aplasma etch process is performed in the process chamber 100 by exposingthe silicon layer to etchants simultaneously with plasma present in theprocess chamber. In one embodiment, operation 214 is performed afteroperation 212 without performing operations 211 and 215. The plasma etchprocess can etch the silicon layer and a portion of thedeposited/treated dielectric layer at the top portion of the trenches toprevent the opening from pinching off. This is because the reaction ofthe etching gas at the top portion of the trenches is typically fasterthan that at the sidewall surfaces, with the bottom surface of thetrenches being the slowest due to a high aspect ratio of the trenches.The plasma etch process will remove the deposited/treated dielectriclayer at the top portion of the trenches at a faster rate than that atthe sidewall surfaces and the bottom surface of the trenches. As aresult, the opening of the trenches is avoided from pinching off and aconformal profile of the dielectric layer can be obtained after theplasma etch process.

The plasma etch process may be performed by introducing afluorine-containing precursor and a carrier gas into the process chamber100. The fluorine-containing precursor and the carrier gas may bepre-mixed and introduced into the process chamber 100 as a gas mixture.In some embodiments, the plasma etch process may be performed in aradical-based ambient, i.e., using radicals from the fluorine-containingprecursor and the carrier gas. Exemplary fluorine-containing precursormay include, but is not limited to, NF₃, F₂, C₂F₆, CF₄, C₃F₈, orsuitable halogenated compound such as SF₆, etc. Suitable carrier gas mayinclude argon, helium, nitrogen, oxygen, nitrous oxide, or any suitableinert gas or carrier gas. In one embodiment, NF₃ and argon are usedduring the plasma etch process. In another embodiment, NF₃ and heliumare used during the plasma etch process. The use of argon as a carriergas has been observed to be able to provide more uniform etch profilesthan helium in some cases. The ratio of the fluorine-containingprecursor and the carrier gas may be in a range of about 1(fluorine-containing gas):6 (carrier gas) to about 1(fluorine-containing precursor):20 (carrier gas), for example about 1(fluorine-containing precursor):10 (carrier gas). In one example, thefluorine-containing precursor is introduced into the process chamber 100at a flow rate of between about 0 and about 500 sccm, such as exampleabout 50 sccm to about 200 sccm, for example about 100 sccm. The argongas is introduced into the process chamber 100 at a flow rate of about 1SLM to about 4 SLM. The plasma etch process may be performed for aperiod of time such as between about 0.1 seconds and about 120 seconds,which may vary depending upon the application. The plasma may beprovided by applying a RF power of between about 100 Watts and about 500Watts, for example about 300 Watts, to the process chamber at afrequency of 13.56 MHz and/or 350 KHz. The chamber pressure may bebetween about 1 Torr to about 40 Torr, for example about 2 Torr andabout 10 Torr, and the temperature of the substrate support in theprocess chamber 100 may be between about 125° C. and about 580° C. whilethe fluorine-containing gas and argon gas are flowed into the processchamber.

The RF power may be provided to one or more electrodes of the processchamber 100. For example, the RF power may be provided to a showerhead,e.g., the gas distribution assembly 120, and/or a substrate support,e.g., the electrostatic chuck 150 of the process chamber 100. In someembodiments, the RF power is pulsed during the plasma etch process toreduce the etch rate of the dielectric layer on exposed surfaces of thetrenches, thereby providing more controllable etching process. The RFpower can be pulsed with a duty cycle in a range from about 5% to about30%, for example about 10% duty cycle, and at a frequency in a rangefrom about 5 kHz to about 30 kHz, for example about 10 kHz. The RF powercan have a pulsing width of about 1 μs to about 50 μs. The RF power maybe adjusted based on the etch time to obtain different etching profilesof the deposited dielectric layer. Table 1 below illustrates examples ofetching profiles of a deposited dielectric layer in a trench afterdifferent plasma etch processes. The following etch and plasmaparameters are used to etch the deposited dielectric layer. Thesubstrate temperature is about 280° C. The chamber pressure is about 2Torr. The flow rate of the fluorine-containing gas (e.g., NF3) is about100 sccm. The flow rate of the carrier gas (e.g., Ar) is about 1000sccm. The pulse width of the RF power is about 10 μs. The RF power canbe pulsed with a duty cycle of about 10%, and at a frequency of about 10kHz.

TABLE 1 Etch time (s) 20 40 40 Power (W) 100 100 300 A: Top sidewall 6.5± 0.3 4.3 ± 0.3 0 thickness (nm) B: Bottom sidewall 3.6 ± 0.2 2.8 ± 0.30 thickness (nm) C: Top surface 13.1 ± 0.2  3.7 ± 0.3 ~0 thickness (nm)Step coverage (B/A) 55% 64% Completely etched Step coverage (B/C) 27%75% Completely etched

As can be seen, higher RF power can increase the etch rate, and thelonger etch time can result in the dielectric layer deposited on topsurface of the trench being etched at a faster rate than that on the topsidewall, with the bottom sidewall being the lowest. Different etch timeand the RF power can be used to adjust the step coverage of thedeposited dielectric layer in the trenches. Longer etch time with higherRF power (e.g., 300 Watts), however, can complete etch the dielectriclayer.

It has been observed that applying RF power pulsing in certain carriergas may result in different etching incubation time (i.e., the amount oftime before etching effect occurs). For example, applying RF powerpulsing in argon gas has shown an etching incubation time of about 2.1seconds. Without RF pulsing, the fluorine-containing precursor in argonor other carrier gas such as helium may result in etching effectoccurred immediately at the deposited/treated dielectric layer.Therefore, the pulsing of the RF power may be adjusted based on thecarrier gas used to control the etching profile. For example, in caseswhere argon is used as the carrier gas, the pulse width of the RF powermay be about 5 μs to about 12 μs, for example about 10 μs. In caseswhere helium is used as the carrier gas, the pulse width of the RF powermay be about 15 μs to about 25 μs, for example about 20 μs. The chamberpressure may be adjusted to enhance the etching effect. For example,when argon is used as the carrier gas, the chamber pressure may be about2 Torr. When helium is used as the carrier gas, a higher chamberpressure, such as about 5 Torr, may be used.

At operation 216, the plasma etch process is terminated and the processchamber is purged to remove the residual etch gas mixture and/or theresidual by-products. The plasma etch process may be terminated byinterrupting the RF power and the flow of the etchants into the processchamber. The purging at operation 216 can be similar or identical tooperation 206.

At operation 218, an optional treatment is performed in the processchamber 100. Operation 218 may be similar or identical to operation 211.The treatment process performed after the plasma etch process atoperation 214 has the additional benefit of passivating defects ordangling bonds on the surface of the etched dielectric layer afterplasma etching.

At operation 220, the optional treatment process is terminated and theprocess chamber is purged to remove the residual gas mixture and/or theresidual by-products. The optional treatment process may be terminatedby interrupting the flow of the silicon-containing precursor into theprocess chamber. The purging at operation 220 can be similar oridentical to operation 206.

The in-situ plasma etch/treatment process 213 may be a cyclic processand repeated multiple times until a desired profile of the depositeddielectric layer is reached.

At operation 222, a decision is made as to determine whether thedeposited dielectric layer that has been treated reaches a desiredprofile, e.g., as-deposited/treated dielectric layer is conformal and/orhas sidewall step coverage in excess of about 95% or 99% without formingvoids or seams in the trenches. If the desired profile has not beenreached, another cycle of the in-situ plasma etch/treatment process 213may be performed (e.g., route 224). In some embodiments, the in-situdeposition/treatment process 203 (e.g., operations 204, 206, 208 and210), operations 211 and 215, and the in-situ etch/treatment process 213(e.g., operations 214, 216, 218 and 220) may be performed (e.g., route225) and repeated multiple times until a target thickness and profileare both reached. The in-situ deposition/treatment process 203 and thein-situ etch/treatment process 213 can repeat multiple times until thedesired film thickness is obtained, for example about 2 to about 6repetitions, for example 4 repetitions, may be performed.

At operation 226, once the deposited/treated dielectric layer reachesthe target thickness and profile, the reactive gases or gas mixtures areturned-off and optionally purged from the process chamber 100. Theprocess chamber 100 is then pumped down (using the vacuum pump 102, forexample) and the substrate is transferred out of the process chamber 100for further processing.

In summary, some of the benefits of the present disclosure providemethods for in-situ deposition, treatment, and etching of a dielectriclayer (e.g., nitride) for improved step coverage. A pulse plasma is usedto form a controllable plasma during the deposition and etching to allowfor deposition and etching of the dielectric layer with enhancedsidewall step coverage without damaging the sidewall film or underlyinglayer. The in-situ process also minimizes cost of ownership, lowers fabspace and faster throughput.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof.

1. A method for processing a substrate, comprising: forming a dielectriclayer on patterned features of the substrate by exposing the substrateto a gas mixture of a first precursor and a second precursorsimultaneously with plasma present in a process chamber, wherein theplasma is formed by a first pulsed RF power; exposing the dielectriclayer to a plasma treatment using a gas mixture of nitrogen and heliumin the process chamber; and performing a plasma etch process by exposingthe dielectric layer to a plasma formed from a gas mixture of afluorine-containing precursor and a carrier gas, wherein the plasma isformed in the process chamber by a second pulsed RF power.
 2. The methodof claim 1, further comprising: exposing the dielectric layer to asilicon-containing precursor after exposing the dielectric layer to thefirst plasma treatment and prior to performing the plasma etch process.3. The method of claim 2, wherein the silicon-containing precursorcomprises silane.
 4. The method of claim 2, wherein the dielectric layeris exposed to a nitrogen-containing gas while exposing to thesilicon-containing gas.
 5. The method of claim 1, further comprisingpurging the process chamber before and/or after the first plasmatreatment.
 6. The method of claim 1, wherein the patterned features aretrenches having an aspect ratio of about 3:1 to about 10:1.
 7. A methodfor processing a substrate, comprising: forming a dielectric layer onpatterned features of the substrate by a plasma deposition process,wherein a first plasma is formed by a first pulsed RF power in a processchamber; densifying the dielectric layer by a plasma treatment; andetching a portion of the dielectric layer by a plasma etch process,wherein a second plasma formed from a gas mixture of afluorine-containing gas and a carrier gas, wherein the second plasma isformed in the process chamber by a second pulsed RF power.
 8. The methodof claim 7, wherein the first and second pulsed RF power has a dutycycle in a range from about 5% to about 30% and a frequency in a rangefrom about 10 kHz to about 20 kHz.
 9. The method of claim 7, wherein thesecond pulsed RF power has a pulsing width of about 1 μs to about 50 μs.10. The method of claim 7, wherein the dielectric layer is siliconnitride.
 11. The method of claim 7, wherein the plasma etch process isperformed in a radical-based ambient.
 12. The method of claim 7, whereinthe fluorine-containing gas of the plasma etch process comprises NF₃,F₂, C₂F₆, CF₄, C₃F₈, or SF₆.
 13. The method of claim 12, wherein thecarrier gas of the plasma etch process comprises argon, helium,nitrogen, oxygen, or nitrous oxide.
 14. The method of claim 13, whereinthe ratio of the fluorine-containing gas and the carrier gas is in arange of about 1 (fluorine-containing gas):6 (carrier gas) to about 1(fluorine-containing gas):20 (carrier gas).
 15. A method for processinga substrate, comprising: forming a dielectric layer on patternedfeatures of the substrate by a plasma deposition process, wherein afirst plasma is formed by a first pulsed RF power in a process chamber;densifying the dielectric layer by a plasma treatment using a gasmixture of nitrogen and helium in the process chamber; forming a firstpassivation layer on the dielectric layer; etching the first passivationlayer and a portion of the dielectric layer by a plasma etch process toform a etched dielectric layer, wherein a second plasma is formed in theprocess chamber by a second pulsed RF power; and forming a secondpassivation layer on the etched dielectric layer.
 16. The method ofclaim 15, wherein the plasma deposition process comprises flowing afirst precursor and a second precursor into the process chamber.
 17. Themethod of claim 16, wherein the first precursor is a nitrogen-containingprecursor comprising ammonia or nitrogen, and the second precursor is asilicon-containing precursor comprising silane or trisilylamine (TSA).18. The method of claim 15, wherein the plasma treatment uses a gasmixture of nitrogen and helium in the process chamber.
 19. The method ofclaim 18, wherein a ratio of the nitrogen and helium in the plasmatreatment is in a range of about 1 (nitrogen):3 (helium) to about 1(nitrogen):10 (helium).
 20. The method of claim 15, wherein the firstand second passivation layers comprise silicon layers.